/*
 *
 * Copyright 2015 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#ifndef GRPC_CORE_LIB_IOMGR_POLLSET_H
#define GRPC_CORE_LIB_IOMGR_POLLSET_H

#include <grpc/support/port_platform.h>

#include <grpc/support/sync.h>
#include <grpc/support/time.h>

#include "src/core/lib/iomgr/exec_ctx.h"

extern grpc_core::DebugOnlyTraceFlag grpc_trace_fd_refcount;

/* A grpc_pollset is a set of file descriptors that a higher level item is
   interested in. For example:
    - a server will typically keep a pollset containing all connected channels,
      so that it can find new calls to service
    - a completion queue might keep a pollset with an entry for each transport
      that is servicing a call that it's tracking */

typedef struct grpc_pollset grpc_pollset;
typedef struct grpc_pollset_worker grpc_pollset_worker;

typedef struct grpc_pollset_vtable {
  void (*global_init)(void);
  void (*global_shutdown)(void);
  void (*init)(grpc_pollset* pollset, gpr_mu** mu);
  void (*shutdown)(grpc_pollset* pollset, grpc_closure* closure);
  void (*destroy)(grpc_pollset* pollset);
  grpc_error* (*work)(grpc_pollset* pollset, grpc_pollset_worker** worker,
                      grpc_millis deadline);
  grpc_error* (*kick)(grpc_pollset* pollset,
                      grpc_pollset_worker* specific_worker);
  size_t (*pollset_size)(void);
} grpc_pollset_vtable;

void grpc_set_pollset_vtable(grpc_pollset_vtable* vtable);

void grpc_pollset_global_init(void);
void grpc_pollset_global_shutdown(void);

size_t grpc_pollset_size(void);
/* Initialize a pollset: assumes *pollset contains all zeros */
void grpc_pollset_init(grpc_pollset* pollset, gpr_mu** mu);
/* Begin shutting down the pollset, and call closure when done.
 * pollset's mutex must be held */
void grpc_pollset_shutdown(grpc_pollset* pollset, grpc_closure* closure);
void grpc_pollset_destroy(grpc_pollset* pollset);

/* Do some work on a pollset.
   May involve invoking asynchronous callbacks, or actually polling file
   descriptors.
   Requires pollset's mutex locked.
   May unlock its mutex during its execution.

   worker is a (platform-specific) handle that can be used to wake up
   from grpc_pollset_work before any events are received and before the timeout
   has expired. It is both initialized and destroyed by grpc_pollset_work.
   Initialization of worker is guaranteed to occur BEFORE the
   pollset's mutex is released for the first time by grpc_pollset_work
   and it is guaranteed that it will not be released by grpc_pollset_work
   AFTER worker has been destroyed.

   It's legal for worker to be NULL: in that case, this specific thread can not
   be directly woken with a kick, but maybe be indirectly (with a kick against
   the pollset as a whole).

   Tries not to block past deadline.
   May call grpc_closure_list_run on grpc_closure_list, without holding the
   pollset
   lock */
grpc_error* grpc_pollset_work(grpc_pollset* pollset,
                              grpc_pollset_worker** worker,
                              grpc_millis deadline) GRPC_MUST_USE_RESULT;

/* Break one polling thread out of polling work for this pollset.
   If specific_worker is non-NULL, then kick that worker. */
grpc_error* grpc_pollset_kick(grpc_pollset* pollset,
                              grpc_pollset_worker* specific_worker)
    GRPC_MUST_USE_RESULT;

#endif /* GRPC_CORE_LIB_IOMGR_POLLSET_H */